1. Field of the Invention
The invention relates to a process for the continuous hydrosilylation of compounds bearing C—C multiple bonds by means of silicon compounds having Si—H groups.
2. Background Art
The continuous hydrosilylation of H-silanes by means of olefins in loop reactors is described, for example, in DE 2851456 C. The reaction proceeds with good mixing and removal of heat. However, incomplete reaction, secondary reactions of the starting materials and backmixing of the products with the starting materials have to be reckoned with.
U.S. Pat. No. 6,350,824 B describes the continuous hydrosilylation of siloxanes, in which a mixture of the starting materials is passed continuously through a tube reactor. Short residence times can be realized in this way. However, the inadequate energy removal in the case of strongly exothermic reactions leads to secondary reactions, hot spots in the reaction zone and difficult reaction control. It is therefore not possible to achieve either a stable process or stable product quality.
WO 03/014129 describes continuous hydrosilylation using a microreaction technique. Noble metal particles from the catalysts used can block the narrow reaction tubes. The reaction is also difficult to control as a result of pressure buildup and pressure drop in the case of siloxanes which have a relatively high viscosity.
U.S. Pat. No. 6,291,622 B describes a combination of a loop prereactor and a downstream tube reactor. The 2 separate parts of the plant result in the need for a great deal of instrumentation for regulation, associated with higher capital and operating costs. Ratios of starting materials are fixed since only a single-stage reaction takes place. Large amounts of reactive starting materials are present in the reaction system, so that elaborate safety precautions are necessary.